The Importance of BTU Per Square Foot

If you’ve ever gone looking for a new HVAC system – or even a window air conditioner or space heater – you’ve probably encountered the initials BTU.

BTU stands for “British Thermal Unit,” and it’s a part of the same system that includes things like pounds or inches, only instead of measuring weight or length, the BTU measures energy.

A BTU is the amount of energy needed to raise the temperature of a pound of water by one degree Fahrenheit at sea level. BTUs allow you to track how much energy an appliance can process to make your space warmer or cooler.

BTU per square foot and determining furnace sizes

Platinum Furnace American Standard

To start with, the appropriate BTU per square foot measurement for your home will depend on where you live. People living in, say, Florida will need a lower number than someone living in Minnesota.

Here in the mid-Atlantic region, you’ll typically need 40-45 BTUs per square foot. To determine the proper furnace size for your home, multiply the appropriate BTU per square foot by the square footage you need to need.

Let’s say you live in a 2,000 square foot home in southeastern Pennsylvania, meaning your BTU per square foot number is at 40-45. That would mean you’d need an 80,000/90,000 BTU HVAC system to heat and cool your home.

BTUs are an important factor in home heating and cooling. Choose a unit with insufficient power, and you’re left feeling too warm in the summer, too cold in the winter and paying a higher than necessary energy bill.

However, there’s more to determining what size heating and cooling unit you need than just BTU per square foot. Consider these factors as well:

1. Your house


In addition to the size of your home, you’ll need to consider some other factors. For example, if your living areas face south, you’ll get more sun – and therefore more heat – in the winter months.

Then there’s the construction of your home. If you’re living in a brick house, you’ve already got more natural insulation than someone living in a home with wood siding.

There are even some external factors that can affect your heating needs. If you’ve got a lot of trees or shrubs planted around your house, you’ll have an extra layer of protection against cold air.

2. Your local climate

House in Maine in Winter

As we indicated earlier, the part of the country where you live can determine the size of the furnace you’ll need. Someone in Maine, with its often brutal winters, would want a bigger, more powerful furnace than someone living in a more temperate climate.

3. Efficiency

Furnaces are required by law to have an efficiency rating of at least 80 percent, and higher-quality heating systems will usually hit 98 percent.

This means two furnaces could be the same size but provide substantially different levels of efficiency. You could purchase a smaller furnace with a higher efficiency rating and still get the same amount of heat as a larger unit with a lower efficiency rating.

Working out which size furnace to choose isn’t something you want to tackle on your own. A qualified HVAC contractor can look at all the factors we’ve discussed here—from home size to efficiency to BTU per square foot – and determine what sort of heating system is right for you.

If you’re preparing to switch to a new heating system, All Seasons Comfort Control can help. For more than 15 years, we’ve worked with Bucks County area homeowners to make sure they’ve had the HVAC service that’s right for them. Contact us today to learn more.